Flameholding apparatus



TSOY K. MOY ETAL March 3, 1959 FLAMEHOLDING APPARATUS Filed April 16,1957 1* Fl G.|-

INVENTORS.

'TSOY KIN MOY FREDERICK W. HENNING W RM ATTORNEY United States Patent2,875,580 FLAMEHOLDIN G APPARATUS Tsoy K. Moy, Kansas City, Mo., andFrederick W. Heuuing, Merriam, Kans., assignors to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication April 16, 1957, Serial No. 653,174 Claims. (Cl. 60-39.72)

This invention relates to jet engines, more particularly to combustionapparatus therefor, and has for an object to provide novel flameholdingstructure for such combustion apparatus.

In jet engines the highly heated and compressed gases travel through theexhaust portion of the engine at relatively high velocities, usuallywell in excess of fifty feet per second. Inasmuch as the rate of flamepropagation in such exhaust streams is less than fifty feet per second,it is impossible to retain a flame formation in such exhaust gasesunless means are utilized to provide a zone or zones of reducedvelocity, in which zones flame formation may be retained.

Many jet engines are equipped with afterburners to provide for burningof additional fuel in the exhaust gases. However, this supplementalburning of fuel frequently occurs only during short intervals ofoperation of the engine, for example, when sudden bursts of speed aredesired as during maneuvering in combat, or for purposes of obtainingadditional thrust during takeoff or wave-off. Most conventionalflameholding. devices presently utilized produce a drag or impedance tothe normal flow of exhaust gases within the exhaust portion of theengine both during afterburning and during non-afterburning operation.Consequently, various attempts have been made to provide flameholderswhich produce less drag or impedance to gas flow when non-afterburningthan when afterburning.

In accordance with the present invention a flameholder is provided whichinvolves the use of one or more pairs of bafiles hingeably joined attheir upstream edges so that they may be separated at their downstreamedges to provide, in effect, a V-shaped structure whose apex is directedupstream, with the result that the V-shaped space thereby provideddefines a zone of stagnancy capable of effecting flame retention. Thepair or pairs of baffles are mounted on a rotary support and means areprovided for rotating this support and the baflles carried therebyduring afterburning operation of the engine. Such rotation of theflameholding apparatus results in outward movement of the outer bafllewith respect to the inner baflle to provide the V-space therebetween.During non-afterburning operation of the engine the flameholding deviceis not rotated and, consequently, with centrifugal forces no longeracting on the outer bafile, it is pushed inwardly against the innerbaffle by the action of the exhaust gases flowing therepast, therebyreducing the effective transverse area of the flameholding structure tothat of a single thin vane or baffie With consequent reduction in dragor impedance thereof.

Accordingly, it is another object of the invention to provideflameholding structure which is moved by cen-' trifugal action tooperative position during afterburning operation of the engine and isreturned to inoperative position during non-afterburning operation ofthe engine by action of the gases flowing therepast.

The foregoing and other objects are effected by the invention as will beapparent from the following description and claims taken in connectionwith the accompanying drawings, forming a part of this application, inwhich:

Fig. 1 is a longitudinal side elevational view, with portions brokenaway for the sake of clearness, and illustrating the aft portion of ajet engine incorporating flameholding structure constructed inaccordance with the present invention;

Fig. 2 is a transverse sectional view taken along the line 11-11 of Fig.1, looking in the direction indicated by the arrows;

Fig. 3 is a fragmentary longitudinal view, partially in section, similarto Fig. l but showing a modified flameholding device;

Fig. 4 is a transverse sectional view taken along the line IV-IV of Fig.3, looking in the direction indicated by the arrows; and

Fig. 5 is a perspective view of one of the flameholding elements shownin Figs. 1 and 2.

Referring now to the drawings in greater detail, and particularly toFig. 1, there is shown the aft portion of a jet engine comprising anouter tubular casing 11 provided at its upstream edge with a flangedconnection 12 with the downstream end of the main engine casing 13, thelatter housing, from front to rear, a compressor (not shown), combustionapparatus (not shown), and a turbine 14.

The exhaust casing 11 may be provided with an inner tubular casing orliner 18, defining an afterburner combustion chamber 19, and spaced fromthe outer casing 11 to provide a passage 20 for flow of cooling airbetween the two casings. The downstream end of the inner casing 18terminates in an exhaust opening 16 whose eifective area may be variedby a suitable exhaust nozzle schematically illustrated at 17. Disposedin the upstream end of the exhaust casing is the usual fairing ortailcone 21 immediately downstream of the turbine 14, and supported fromthe outer casing 11 by the struts 22.

A shaft 26 is journalled in the downstream end of the tailcone 21, as at27, and is coaxial with the tubular casings 11 and 18 and extendsdownstream beyond the tailcone 21. Secured on the extending portion ofthe shaft 26 is a hub member 28 carrying a plurality of radiallyextending arms 29 at the free ends of which are mounted inner baffles31, preferably disposed parallel to the axis 7 of rotation of the shaft26.

As illustrated in Fig. 5, the inner baffle 31 is rectangular and hasassociated therewith an outer baflie 32 of similar shape, the twobaffles being joined at their upstream edges by a pin 33 passing througheyelets 34 and 35 provided on the inner and outer bafiles, respectively.With this construction, the outer baffle 32 is free to move between afirst position, indicated by dotted lines in Figs. 1 and 5, where itclosely abuts the inner baflle 31 and a second position where it is at asubstantial angle with respect to the inner baffle, as illustrated bysolid lines in Figs. 1 and 5, in which latter position there is providedbetween the two baflles a V-shaped space or zone 36 serving to anchorany flame formation produced in the afterburner combustion chamber.

Preferably suitable means, such as the lug 37, is provided for limitingthe outward movement of the outer bafile 32 with respect to the innerbaflle 31.. While in the construction illustrated in Figs. 1, 2 and 5,four such pairs of inner and outer baflles are shown, it will beapparent that a greater or lesser number may be utilized as founddesirable.

Afterburning fuel is admitted to the upstream end of the afterburnercombustion chamberthrough the conduit 41 and the annular series ofnozzles 42 associated there-' with. Suitable means, such as the ignitor43, is provided downstream thereof to ignite the after-burner fueladmitted through the conduit 41 and nozzles 42.

Housed within the tailcone 21 is a suitable motor 45 which may be of anydesired type, for example, an electric motor or an air motor, providedwith motive power through conduits 46 disposed in one of the struts 22which is formed hollow for the reception of these conduits. The motor isconnected through suitable shafting and gearing with the shaft 26 whichcarries the flameholding structure, and serves to rotate the latterduring afterburning operation of the engine. As previously mentioned,rotation of the flamehol'der results in the centrifugal forces which actupon the outer baffles 32 moving the latter outwardly to provide thefiameholding zones 36 between the inner and outer bames. When theafterburning operation is ended, the motor 45 will be shut off and withthe afterburner no longer rotating, the forces of the gases flowing pastthe flameholder will-force the outer baffles 32 inwardly against theinner baffies 31 to reduce and substantially eliminate the drag effectof the fiameholding structure.

The motor 45 may be of a variable speed type, and variations in thespeed thereof will result in corresponding variations in the centrifugalforces applied to the outer battles 32. Consequently, by varying thespeed of the motor 2-5, the effective fiameholding area of the bafflesmay be varied as desired, as with change in altitude of the plane.

In Figs. 3 and 4, there is shown a modified form of fiameholder whichdiffers from that described above only in that the flameholdingstructure is substantially con tinuous circumferentially with the innerbaffie being comprised of a single annular baflle 31a to which arepivotally secured a substantially continuous series of outer baffles32a. It will be apparent that this form of fiameholder operates in thesame manner as that of the previous modification, the outer bafflesbeing moved outwardly due to centrifugal action when the flameholdingstructure is rotated and being moved inwardly against the inner bafflesby the exhaust gases flowing therepast when the fiameholding structureis stationary during non-afterburning operation of the engine.

While the invention has been shown in several forms, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various other changes and modifications without departingfrom the spirit thereof.

What is claimed is:

1. Combustion apparatus comprising Wall structure defining a flow pathfor a high velocity combustible mixture; and fiameholding apparatusdisposed in said flow path for creating a degree of stagnancy thereinsufiicient to effect flame retention; said fiameholding apparatuscomprising first and second members pivotally connected adjacent theirupstream edges, considered in the direction of flow in the flow path,means mounting said members for rotation in a plane transverse to thedirection of said flow, said first member being carried by said mountingmeans and said second member being disposed radially outward of saidfirst member, whereby during rotation of said mounting means and saidmembers, said second member may pivot outwardly about the pivotalconnection with said first member and provide with said first member asheltered zone downstream thereof.

2. For use with combustion apparatus through which a stream ofcombustible mixture is adapted to flow at velocities in excess of therate of flame propagation therein; fiameholding apparatus for producingin the stream of combustible mixture a degree of stagnancy sufficient toeffect flame retention, said fiameholding apparatus comprisingsupporting structure fixed with respect to the combustion apparatus,ashaft journalled in said supporting structure with its longitudinalaxis parallel to the direction of flow of combustible mixture throughthe combustion apparatus, an arm secured to, and rotatable with, saidshaft within said combustion apparatus, and a V-shaped structure carriedby said arm with the point of the V disposed upstream with respect tothe flow of the stream of combustible mixture, said ti-shaped structurecomprising a pair of baflles constituting the legs of the V andpivotally connected at the point of the V, the radially inner one ofsaid baffies being secured to the arm and the radially outer one of saidbafiies being free to pivot between a first position where it closelyparallels said inner baflie and a second position where it forms a Vwith said inner baffle.

33. In combustion apparatus for a jet engine; tubular casing structuredefining a combustion chamber adapted to receive a high velocity streamof combustible mixture, supporting structure mounted in the casingstructure, a shaft rotatably mounted in the supporting structure withits axis of rotation generally parallel to the direction of flow of thestream of combustible mixture through the combustion chamber, a hubsecured on said shaft and rotatable therewith, a plurality of armsextending outwardly from said hub, and fiameholding structure carried bysaid arms and disposed in the flow path of the combustible mixturestream, said flameholding structure comprising radially inner bai'llestructure secured to said arms and radially outer baffle structurepivotally connected to the inner baifie structure for limited movementwith respect to the latter between a non-flameholding position Where thebafile structures are substantially parallel to each other and afiameholding position where the baffle structures are disposed at asubstantial angle to each other with the apices of the angles disposedupstream, thereby providing V-shaped sheltered zones for flame retentionduring combustion of the combustible mixture in the combustion chamber.

4. In combustion apparatus for a jet engine; tubular casing structuredefining a combustion chamber adapted to receive a high velocity streamof combustible mixture, supporting structure disposed in said combustionchamber, a shaft rotatably mounted in said supporting structure with itsaxis of rotation generally parallel to the longitudinal axis of thetubular casing structure, a hub carried by and rotatable with saidshaft, a plurality of arms extending generally radially outward fromsaid hub, first flat baflles secured to the free ends of said arms, saidfirst bafiles lying in planes generally tangential to the axis of theshaft, second flat baffles associated with the first baffles, meanspivotally joining pairs of associated first and second baffles at theirupstream edges to provide hinge-like structures, and means for rotatingthe shaft and the baffle structure carried thereby, the second baffle ofeach hinge-like structure being pivotable radially outward under effectof centrifugal forces during rotation of the shaft to provide V-shapedsheltered zones at the downstream side of the hinge-like structures.

5. In combustion apparatus for a jet engine; tubular casing structuredefining a combustion chamber for a high velocity stream of combustiblemixture, supporting structure disposed in the casing structure, a shaftrotatably mounted in said supporting structure with its axis of rotationsubstantially parallel to the longitudinal axis of the tubular casingstructure, a hub carried by and rotatable with said shaft, a pluralityof arms extending outwardly from said hub, an inner baffle membercarried by said arms, outer bafile members associated with said innerbafiie member, means pivotally joining said inner and outer bafflemembers at their upstream edges, whereby said outer bafiie members mayswing outwardly at their downstream edges from the inner baffle memberto define between the inner baffle member and the outer baffle membersV-shaped sheltered zones, and means for rotating the shaft and thebaffle members, whereby centrifugal forces will effect outward movementof said outer baffle members to effect the V-shaped sheltered zones. 1

References Cited in the tile of this patent UNITED STATES PATENTS

